Despite recent advances in elucidating the composition of chylomicrons and very low density lipoproteins, little is known concerning the quantitative aspects of intestinal apoprotein synthesis and factors which modulate this process. In addition, the recent knowledge that the intestine may be a quantitatively important synthetic site for certain chylomicron apoproteins and contribute to plasma levels of these apoproteins, makes an understanding of intestinal lipoprotein formation and secretion of importance. We therefore propose to quantitate chylomicron apoproteins within intestinal epithelium during varying conditions of lipid feeding and correlate these findings with chylomicron composition and apoprotein secretion rates in mesenteric lymph. These studies will be conducted using the mesenteric lymph fistula rat. In addition, the effects of various dietary lipids on chylomicron composition and secretion will be directly tested in 2 patients with chyluria. Individual chylomicron apoproteins (apoB,A-I, A-IV,E) will be purified from rat mesenteric lymph and chylous urine. Monospecific antisera will be produced and radioimmunoassay procedures developed for the direct quantitation of these apoproteins in intestinal mucosa. The effects of saturated and unsaturated lipids, and cholesterol on intestinal apoprotein content and synthesis will be determined directly on rat intestinal mucosa and in human intestinal biopsies. These findings will be correlated with chylomicron apoprotein composition and apoprotein secretion rates in rat mesenteric lymph-as well as in two patients with chyluria. The redistribution of chylomicron apoproteins (apoA-I,A-IV) after secretion will be studied by in vitro incubation techniques as well as chylomicron infusion experiments into rats. These studies should provide informtion concerning factors which modulate the intestinal contribution to lipoprotein metabolism.